This invention is generally concerned with a system for widening a highway flanked by irregular terrain and for providing support for a sound wall.
Systems for widening highways flanked by irregular terrain are known in the prior art. Such systems may be used, for example, on highways paved along a ridge-like formation where the grade of the terrain drops off sharply from the sides of the highway, or where a highway is paved at the bottom of a gully-like depression where the terrain slopes sharply upwardly from the highway sides. More commonly, such systems are used to widen highways paved along the sides of hills or mountains where the terrain slopes upwardly on one side and downwardly on the other.
Such widening systems generally involve the installation of a retaining wall for retaining either a cut face of earth or fill material. In cases where the terrain slopes upwardly from the side of the highway, the ground is leveled by bulldozers and the like by cutting away and removing the earth adjacent to the flank of the highway. The retaining wall is then installed in order to retain the cut face of earth. The highway is then widened over leveled ground adjacent to the retaining wall. In cases where the terrain slopes downwardly from the highway, bulldozers and the like are used to cut a step or terrace in the earth along the line that is parallel to and spaced apart from the side of the highway. The retaining wall is then installed along the step or terrace, the wall being raised to at least the level of the highway. Fill material is then packed between the highway and the adjacent face of the retaining wall to level the terrain between these two points. Because of the large moment forces that such retaining walls are subjected to in holding back either a cut face of earth or compacted fill material, the bottom ends of such walls are often structurally connected to massive, steel reinforced foundations that are many times wider than the thickness of the wall sections. The use of such massive foundations necessitates the use of a substantial amount of materials and labor. Additionally, the deep and wide excavation necessary for the installation of such a foundation can make it difficult to limit the disruption of the terrain to only the area of the highway right-of-way (particularly where such right-of-way is narrow), and can result in the unwanted destruction of trees, creeks, and other environmental assets.
Acoustical wall systems for obstructing highway noises from residential areas are also known in the prior art. Such wall systems generally take three different forms, including self-supporting walls, monolithic post and panel precast walls, and post and panel precast walls. Of these three types of wall systems, post and panel acoustical walls are among the most adaptable for use on irregular terrain. Such acoustical walls employ panels that are slidably mounted and supported by structurally independent support posts. The support posts are typically steel or concrete columns having opposing pairs of flanges which slidably receive the side edges of the wall panels. During construction, a wall panel is raised by a crane above two adjacent support posts, and subsequently lowered between the posts after the side edges are aligned between the flange pairs. Either a single panel or a stack of panels may be mounted between two adjacent posts, thereby imparting valuable adjustability with respect to the height of the completed wall. With such a system, it is relatively easy to create a sound wall having a uniform height along a highway where the terrain varies in height either beside or in the direction of the highway.
Despite such advantages over other types of sound walls, post and panel walls also have their disadvantages. One major disadvantage stems from the necessity of having to leave some amount of slack in the distance between the flanges of the support posts and the thickness of the side edges so that the panels may be quickly aligned between the flanges and the beams prior to slidably lowering them between two flange pairs of adjacent posts. As a result of this slack, the front side edges of the panels cannot snugly engage the front flanges of their respective support posts, which if not corrected will create substantial acoustical leaks in the resulting wall, and poor structural alignment of the panels. In the past, this slack has been eliminated by the installation of steel angle members between the back flanges of the support posts and the back side edges of the panels to take up the unwanted slack. Unfortunately, the installation of such steel angles has proven to be an expensive and time consuming step in the assembly of such wall systems, as it requires the drilling of a specific pattern of holes through the flanges of the I-beams forming the support posts, the regalvanization of the I-beams, as well as the tedious installation of several nuts and bolts for every angle in such a way that they continuously apply pressure to the back side edges of the panels. Worse yet, the use of such steel angle members sometimes fails to permanently remove unwanted slack between the front side edges of the panels and the flanges of the posts because of the constant vibration that such wall systems are subjected to due to their proximity to a heavy flow of road traffic.
Combined retaining wall and sound wall structures are also known in the prior art. In such combined structures, a sound wall system is installed on top of the retaining walls used to retain either a cut face of earth or a fill material incident to a highway building or widening operation. Since additional moment forces may be applied to the retaining wall as a result of high winds blowing on the sound walls, the retaining walls in such a combined structure must be redesigned to accommodate these additional moment forces. In the past, this has been done by simply enlarging the already massive foundation slab that the retaining wall is connected to, and by further increasing the thickness of the wall sections. However, such a design solution considerably increases the already considerable amount of materials and labor necessary to construct the retaining wall, and requires an even larger excavation to construct.
Clearly, there is a need for an improved combination retaining wall and sound wall for widening a highway flanked by irregular terrain that overcomes the disadvantages associated with the prior art. Ideally, such a combination structure would be capable of bearing all of the moment forces exerted on the retaining wall plus the moment and compressive loads exerted by the acoustical sound wall without the need for substantial enlargements in the size of the retaining wall foundation or the thickness of the wall sections. Such a combined structure should further require only a very narrow strip of terrain for installation to maximize the use of relatively narrow highway right-of-ways, while minimizing the amount of excavation, filling, and other disruptions around the right-of-way. Finally, such a combined structure should utilize a post and panel sound wall having an alternative slack-removing means that does not necessitate the time consuming drilling of holes in the I-beams and installation of steel angles between the wall panels and the flanges of the posts.